Impulse turbine



Jan. 31, 1956 P. F. DANEL 2,733,044

IMPULSE TURBINE Filed June 26, 1951 4 Sheets-Sheet l INVENTOR. Ear/vWant Z 1 74 BY W HTTOR VEY Jan. 3 1956 P. F. DANEL 2,733,044

IMPULSE TURBINE Filed June 26, 1951 4 Sheets-Sheet 2 uvmvron. iz'errzJana! 4 7 TOP/V5 Y Jan. 31, 1956 P. F. DANEL 2,733,044

IMPULSE TURBINE Filed June 26, 1951 4 Sheets-Sheet 3 I 7 f z 10 g Zg g 55 8 PRIOR fllxT 40 :z/WW/W,

INVENTOR.

BY Farr! Fjaw/ AITTl/RIVEY Jan. 31, 1956 P. F. DANEL 2,733,044

IMPULSE TURBINE Filed June 26, 1951 4 Sheets-Sheet 4 INVENTOR. fill ffFla/1e! HTTUIPNE) IMPULSE TURBINE Pierre F'rangois Darrel}, Grenoble,France, assignor to E tablissem'ent'stNeyrpic, Grenoble, France, acorporation of France Application June 26, 1951, Serial N 0. 233,522Claims priority, application France July 17,1950 15 Claims. (Cl. 253-24)The present invention relates to impulse turbines, and particularly toapparatus for supplying water to such turbines' including nozzlestructures and piping arrangements leading thereto.

In impulse turbine installations, the form and arrangement of thedifferent parts of the water supply apparatus is arrived at by acompromise between the ideal structures which would produce the bestefiiciency and the necessities of'constr'uction and installation.

In particular, the flow of water from the end of the water supplyconduit to the injector nozzle poses a delicate problem. For a givenvolume rate of flow, it is well known how to construct a conduit whichwill have very high elficiency. However, such conduits, besides having apoor esthetic appearance, usually have large space requirements whichare not compatible with the best economy, either from the point of viewof the supporting building structures required, or from the point ofview of the mechanical construction of the conduits themselves.

The best etficiency would be obtained by providing a straight conduitsection of substantial length immediately upstream from the injectornozzle. Such an arrangement is generally impossible. In particular, inall those cases where. the injectors include needle valves operated fromtheexterior through a valve stem, the body of the injector mustnecessarily have an elbow in order to permit the passage of the valvestem to the exterior. The

' presence of an elbow or curve always results in a disturbance of theflow due to the separation of the water from the internal: wall of theelbow and to secondary currents produced by the rotation of the liquidstream. This disturbance of the flow has the effect of reducing thechiciency of the turbine and thereby produces a loss of energy muchgreater than the loss of head within the elbow.

In; practice, the location of injectors and their water supply conduits,with elbow-type injector nozzles of the previously known types, isdetermined by the following limiting. conditions 1 1.. The ratio of themean radius R of the injector elbow to the diameter 5 of the body of theinjector may not be. decreased below a certain value which increases asthe angle through which the stream is turned increases, without;resulting in an undue disturbance of the efficiency. For:v 90 elbows,for example, the ratio should not be less than approximately 2.

2. Even though the ratio of an elbow type injector is sufficientlygreat, it is neces- I sary to locate a spider of radial vanesimmediately upstream from the nozzle opening so as to eliminate as farbut the number of the spider guide vanes and their length in thedirection of flow are determined, not by the mechanical requirements fortheir support, of the valve stem, but by the necessity of redirectingthe secondary currents.

3. In machines having a horizontal axis or a vertical axis with multiplejets, the angle between two injectors may not be reduced below a certainvalue without a corresponding reduction in the efiiciency.

it these three conditions are satisfied, a machine of very goodefiiciency will be produced.

Unhappily, the search for maximum efliciency results in water supplystructures which are not very esthetic (which is not serious). Moreoften such structures are very bulky, which is very serious when oneconsiders their cost as well as the size and cost of the supportingstructure required.

The present invention provides, in place of the ordinary elbow usuallyemployed, an elbow provided with guide vanes which extend substantiallythroughout the length of the elbow and perpendicular to the plane, whichbisects the elbow longitudinally.

it is desirable to make the elbow convergent in order thata small numberof guide vanes may produce a flow which does not separate from the wallsof the conduit and does not rotate within the conduit. For example, fora elbow including three guide vanes, and having a mean radius equal tothe diameter of the outlet, the optimum convergence is approximately 25to 30% of the inlet cross-section, but this may be reduced toapproximately 10% while still maintaining acceptable flow conditions.

The guide vanes separate the elbow into a certain number of elementarychannels. Only the channels situated on the outer side of the elbow (andthe middle channel if an even number of guide vanes is used) are crossedby the stem of the valve, but the latter is at a very oblique angle withreference to the principal direction of the current in these channels,so that the section of the valve stem taken perpendicular to thedirection of the current presents the form of an elongated ellipse andconsequently has a hydrodynamic profile which produces very littledisturbance of the flow.

In accordance with the invention, there may be pro vided within thechannels which are traversed by the needle valve stem, at fairing orstreamlined housing oriented along the plane which bisects the elbowlongitudinally and extends to the vicinity of the downstream end of theguide vanes.

Such a streamlined housing could of course be supplied in an elbow typeinjector of conventional form, but in such a structure it would be oflittle or no effect because of the presence of secondary currents.

In an elbow constructed in accordance with the invention, the guidevanes cooperate with the convergence to produce a flow which is freefrom separations and from secondary currents which may be injurious,even though the ratio of the elbow may have a value substantially lowerthan the limiting value used in the case of conventional structures.

Because of the fact that the secondary currents at the outlet of theinjector elbow are negligible, the vane spider at the outlet actsessentially only as a support or guide for the. stem of the needlevalve. The number and the length of the spider vanes may be reduced tothe minimum required to insure the proper support of that stem.Alternatively, it is possible to completely eliminate the spider. Theguide bearing for the stem of the needle valve is then directlysupported by the guide vanes of the elbow and by the streamlined housingadjacent the needle valve stem. In this case, it is desirable to locateone of the guide vanes so that its trailing edge will be aligned withthe axis of the needle valve stem.

It is often necessary, in order conveniently to connect a certaininjector nozzle to the water supply conduit, to locate a second elbowupstream from the injector elbow. Whenever a conduit includes twoconsecutive elbows, there is a tendency to produce a rotation en masseof the fluid at the outlet of the downstream elbow, the injurious effectof that rotation being added to effects of the secondary currents.

The intensity of that rotation depends on several factors such as thelength of the straight conduit between the two consecutive elbows, thesupply conditions of the as sembly, and the angle between the planes ofthe two elbows if they are not located in the same plane. However, theseelements are not subject to control by the designer, because they areestablished by the general conditions of the installation; furthermore,the difficulties pro duced in a given arrangement may not be exactlypredicted.

In an installation comprising an elbow at the injector equipped withguide vanes in accordance with the present invention, the operatingconditions are greatly improved, regardless of the orientation of thesecond elbow with reference to the injector elbow. Under theseconditions the flow from the outlet of the injector elbow has only avery small rotation en masse and very small secondary currents.

These conditions of operation may be further improved by equipping thesecond elbow with guide vanes and making it convergent.

It has been pointed out above that it is desirable to provideconvergence of either the elbow at the injector, or a second elbowupstream from the injector. It may be objected that for the samediameter of the body of the injector nozzle, such a convergence wouldincrease the diameter of the piping upstream and consequently of thesafety valve, although economy requires that the diameter be as small aspossible.

Since the mean radius of the injector elbow is reduced by the use of thepresent invention, and since spacing of the injector elbow and theupstream elbow are not determined by hydraulic considerations, it ispossible to utilize the structures shown and claimed in my copending U.S. application Serial No. 233,521, filed January 26, 1951. in such astructure, each elbow is preceded by a straight divergent length ofconduit. This construction permits the diameter of the water supply pipeor of the manifold for the turbine to be made as small as or evensmaller than that required by conventional constructions.

Finally, the water supply connections of multiple jet impulse turbinesinclude several branch connections. It is well understood that it isdesirable to give these branch connections a form which in itself has agood hydraulic efficiency, for example, the form described and claimedin U. S. Patent No. 2,533,720, dated December 12, 1950. The patent showsa branch connection where the ridge dividing the two downstream branchesis placed in the full current, that construction being obtained by thelateral displacement of the axes of the outlets with respect to the axisof the inlet.

The convergent injector elbows having guide vanes conforming to thedescription above, may be combined with one or the other or both of thestructures described in U. S. Patent No. 2,533,720 and in theapplication Serial No. 233,521 referred to above. It is thereforepossible to construct manifolds or water supply piping for impulseturbines presenting one or several of the following advantages:

1. Improved hydraulic operation; that is to say, improvement of theefficiency of the turbine.

2. Reduction of the weight and the space requirements of the completeturbine and also the cost of the water supply piping. This reduction inthe space requirements results in a corresponding reduction in the costof the supporting structures and certain apparatus suchas travelingcranes.

3. Reduction in the diameter at the inlet of the manifold andconsequently the diameter of the safety valve and its cost.

In order more completely to explain the invention and the results whichmay be obtained through its use, several embodiments thereof areillustrated in the annexed drawings:

Fig. 1 is a cross-sectional view taken along the line II of Fig. 2 of anelbow type injector constructed in accordance with the invention.

Fig. 2 is a cross-sectional view taken along the line iI--II of Fig. 1.

Fig. 3 is a cross-sectional view taken along the line lIL-III of Fig. 1.

Fig. 4 is a cross-sectional viewsimilar to Fig. 1, showing a modifiedform of elbow type injector according to the invention, taken along theline IVIV of Fig. 5.

Fig. 5 is a cross-sectional view taken along the line V-V of Fig. 4.

Fig. 6 is a schematic elevational view of a conventional horizontalimpulse turbine.

Fig. 7 is an elevational view similar to Fig. 6, showing the sameturbine equipped with water supply apparatus constructed in accordancewith the invention.

Figs. 8 and 9 are schematic elevational views showing different forms ofwater supply apparatus embodying the invention which may be used for thesame turbine as Fig. 6.

Fig. 10 is a schematic plan view of a vertical axis impulse turbine ofconventional type.

Fig. 11 is a schematic plan view of the same turbine as in Fig. 10,equipped with water supply apparatus constructed in accordance with theinvention.

Fig. 12 is a schematic plan view of a modified form of the inventionwhich may be applied to the turbine of Fig. 10.

Fig. 13 is a fragmentary elevational view of water supply piping andinjectors constructed in accordance with the invention for a verticalimpulse turbine having four nozzles, one of the nozzles being brokenaway.

Fig. 14 is a plan view of the water supply piping of Fig. 13.

Fig. 15 is a plan view of a modified form of water supply pipingconstructed in accordance with the invention for a vertical impulseturbine having four jets.

Referring to Figs. 1 to 3, there is shown a nozzle tip 1 connectedthrough a casing 2 to the outlet of an elbow 3. Within the elbow arethree concentric guide vanes 4, 5 and 6. Within the casing 2 is a flowdirecting spider of radial vanes 7. Supported centrally of the radialvanes 7 is a guide bearing 8 for the stem 9 of a needle valve 10.Apparatus for operating the needle valve is shown diagrammatically at11. A streamlined housing or fairing 12 on the downstream side of thevalve stem 9 helps to smooth the flow at that point.

The three concentric guide vanes 4, 5 and 6 divide the flow into fourconcentric channels, and tend to redirect any rotary component of flowwhich may appear. The spider vanes 7 have a further redirectinginfluence.

The elbow 3 is convergent, since its inlet is wider than its outlet, asshown in Fig. 2. This further improves the hydraulic flowcharacteristics of the elbow.

It should be noted that, as compared to conventional elbow-typeinjectors, the structure shown in Figs. 1 to 3 has a very short radiusapproximately 1) and that the spider vanes 7 are very much shorter inthe direction of flow. The spider vanes 7 are made only as long asrequired to give the guide bearing 8 its necessary length.

An injector elbow may be constructed in accordance with the invention byany convenient known method. It may for example be constructed in twoparts, with the plane of the joint being the plane of the section shownin Fig. 1'.

Figs. 4 and 5 illustrate a modified form of elbow-type injectorconstructed in accordance with the invention. In these figures, partswhich'are similar to their counterparts in Figs. 1-3 have been given thesame reference characters and will not be further described.

In Figs. 4 and 5, the needle valve stem 9 is guided by a bearing 13supported partly on the central guide vane 5 and partly on the fairing12. A casing 14, muchshorter in length, replaces the casing 2 of Fig. 1.The spider with its radial vanes is completely eliminated, reliancebeing placed wholly on the vanes 4, 5, 6 and the convergence of theelbow to maintain good hydraulic flow characteristics.

l-n-Fig'. 6 there is shown schematically a horizontal impulse turbine 15having. two nozzles 16 and 17 equipped with conventional elbow-typeinjectors 18 and 19.

The upper nozzle 16 is located at an angle A with the horizontal, and issupplied through a 90 elbow 18 with a ratio of approximately 2, which isthe minimum value permissible for a conventional 90 elbow. A casing 18acontaining a flow straightening spider (not shown) has a length which isof the same order of magnitude as its diameter. The lower nozzle 17 ispositioned at an angle B with the horizontal. The angle between the twoinjectors is C. The axis of the shaft 20 of the machine is located atthe level The axis of the outlet of a water supply pipe 21 is located atthe level h. The levels H and h are determined by the general designrequirements of the plant. A safety valve 22 having a diameter D islocated between the outlet of pipe 21 and a branch connection 23. Thenozzles 16 and 17 are provided with valve operating mechanisms 16a and17a, respectively.

The space requirements of such an impulse turbine may be. measured bythe distance L between the vertical through the axis of the shaft 20 ofthe turbine and the downstream outlet of the safety valve 22. Thelocation of the branch connection 23 is determined by the selection ofH, h, angle A and the angle (90) of the injector elbow, which latteralso determines the choice of Figs. 7 and 8 show two alternative formsof water supply apparatus for the turbine 15 of Fig. 6, under the sameconditions of spacing of the injector nozzles and the same levels of theaxis of the turbine and of the axis of the supply conduit, but with anupper injector elbow 24 constructed in accordance with the invention.The lower injector 17 and its related parts may remain the same as inFig. 6.

The ratio 5 9 of the injector elbow 24 is approximately 1. The casing 25containing the spider is much shorter than casing 18a.

much: closer to the axis 20 of: the turbine than. in; the ease of Fig.6. The spacing L of an apparatus constructed in accordance with theinvention as illustrated in. Fig. 7 is about two-thirds of the spacing Lof a conventional arrangement. The improvement in weight which resultsin the piping and in the injector elbow is of the order of one-third.

Fig. 8 illustrates a modified form for use where economy in themechanical parts is very essential. In this case there is provided adivergent pipe section 27 between the connection 23 and' a safety valve28, connectedto the outlet of a supply pipe 29. The apparatus of Fig; 8.has the same spacing requirement L as the apparatusof Fig. 6. However,the addition of the divergent pipe section 27 to the structure of Fig. 7allows'theuse of a safety valve 28 whose diameter d is no more thantwo-thirds of the: di-

ameter D of the safety valve of Fig. 6. Theembodiment in Fig. 8 presentsa further advantage over that of Fig. 6

in the form of a reduction of approximately one-fifth in the weight ofthe piping and the injector elbows.

it should be understoodv that the invention includes com.- promiseconstructions, between those shown in Figs. 7 and 8, which constructionsmay provide botha reduction. in the spacing requirements and in thediameter of'the safety valve. Such compromise constructions may bevaried as required to suit the needs of each installation.

Where it is necessary to reduce the spacing requirement L to theminimum, the embodiment of the' invention shown in Fig. 9 may be used.This embodimentincludes a branch connection 30' immediately upstreamfrom the injector elbow 24. This arrangement requires that the axis ofthe supply conduit 33 be raised to a level h higher than it, and thatthe lower nozzle 17 be provided with an elbow 31 having a greater angleand a smaller ratio The lower elbow 31 is therefore also constructed. inaccordance with the present invention, being made convergent andprovided with guide vanes.

The spacing L" is no more than five-eighths of the spacing Lcorresponding to the case of Fig. 6, but the diameter D of the safetyvalve 32 and the diameter of the supply pipe 33 are greater.

There is shown in Fig. 10 a schematic plan view of a vertical axisimpulse turbine generally indicated at 34 including two injector nozzles35 and 36 of conventional type. A casing 37 forms the supportingframework for a generator (not shown) located above the turbine. Theinjector nozzles 35 and 36 project within the casing at diametricallyopposite points. The elbows at the injectors and the piping connectingthem with a supply conduit 38 are in the horizontal plane of the rotor39 of the turbine. The supply conduit 38 leads through a safety valve 40to a branch connection 41. The construction shown in Fig. 10 requires adistance M between units and a spacing N between the walls of the hydroelectric station.

Figs. 11 and 12 show schematically two embodiments of water supplyapparatus for theturbine 34 constructed in accordance with the presentinvention.

In these two embodiments, it is assumed that it is desirable to retainthe same form of the casing 37 and the same direction of the supplyconduit 38.

In the arrangement shown in Fig. 11, the water flows from the safetyvalve 40 through a branch connection 41 of the type shown in my U. S.Patent No. 2,533,720, previously identified. Thence 'it passes eitherthrough a straight divergent pipe section 42, and, consecutive .elbows43 and 44, and pipe 45 to a nozzle 46 or through a straight divergentpipe section 47', consecutive elbows 48 and 49, and pipe 50 to a nozzle51. All the elbows are convergent and provided with guide vanes. Theguide vanes in elbows 43 and 48 are prolonged upstream 7 from the guidevanes in the elbows 44 and 49. All the elbows and piping are in thehorizontal plane of the rotor 39.

As compared to the arrangement shown in Fig. 10, the arrangement of Fig.11 presents the advantage of reducing the interaxial spacing Ma. betweenadjacent units. The spacing IIn. between the walls of the station isalso reduced approximately one-fifth and the weight of the injectors andthe piping is reduced approximately twothirds.

With reference to Figs. and 11, it may be noted that in order to reachthe nozzles such as 46 and 51 within the casing 21, the straight pipessuch as 45 and 50 in Fig. 11 must have a substantial length.

In the embodiment shown in Fig. 12, a very compact spacing is attainedby providing the nozzles 46 and 51 with 90 elbows 52 and 53,respectively, located within the interior of the casing and in verticalplanes. These 90 elbows are convergent and provided with guide vanes andare connected with straight divergent (not shown) sections extendingvertically within the casing 37. These straight sections are in turnconnected with elbows 54 and 55 respectively, located Within casing 37and connected through straight divergent sections 56 and 57,respectively, to the outlets of branch connection 58. All theconnections up to the branch connection 58 are placed within theinterior of the casing 37, from which the branch'connection 58 projectsthrough an opening provided for that purpose.

The spacings Mb and Nb and the weight of the piping are again reduced inthe structure of Fig. 12 by comparison with the structure of Fig. 11.

Apparatus in accordance with the present invention is particularlydesirable for vertical axis impulse turbines having multiple jets. Theconventional arrangement generally adopted for such turbines consists inproviding a manifold, which extends almost completely around the turbineoutside the casing and from which branches depart successively towardthe several injector nozzles. The manifold may be within the plane ofthe rotor or in a lower plane, but in either case, its construction andmounting present difiicult problems. The spacing required in the planeof the manifold is great and the presence of the manifold complicatesthe operation of changing the rotor. The rotor must be lowered to aconsiderable extent in order to be disengaged laterally, particularly inthose cases where the manifold is in a plane lower than that of therotor itself.

When the manifold is in the plane of the rotor, it is necessary that theapparatus for operating the needle valve of each injector nozzle extendacross the manifold. Since the cross-section of the latter decreasesfrom one injector to the next, the several injectors are necessarily alldifferent.

In the modification of Figs. 13 and 14, four identical injector nozzles59 (only three of which appear in Fig. 13) are each provided withconvergent elbows 60 having guide vanes. These elbows are connected byindividual pipes to a convergent branch connection 61 having fourbranches, which is supplied through a stop valve 62. The several pipesare formed of straight divergent elements such as 63, 64, 65, 66 and 67and of convergent elbows with guide vanes such as 68.

In Figs. 13 and 14 the four injector nozzles 59 are regularly spacedaround the axis of the turbine. It should be understood that it is ofadvantage to combine that structure with the arrangement shown andclaimed in U. S. patent application of Pierre S. Duport, Serial No.232,495, filed June 20, 1951, in which the injector nozzles areconcentrated in a limited angle about the turbine axis.

Such a construction is shown in Fig. 15, where a supply conduit 69discharges through a stop valve 70 located in a plane below that of therotor, and thence through a convergent branch connection 71 having threeoutlets.

One of these outlets directly supplies a nozzle 72; another outlet ofequal cross-section feeds a nozzle 73 through a straight divergentelement 74 and a convergent elbow 75 having guide vanes; the thirdoutlet has a cross-section twice that of the other two and dischargesinto a straight divergent section 76 and thence through a branchconnection 77 having two outlets, one leading directly to a nozzle 78and the other to a nozzle 79 through a straight divergent conduitelement 80. The nozzles are all provided with convergent elbows of theguide vane type. The nozzles 73 and 79 may be duplicates and nozzles 72and 78 may also be duplicates.

Except for the two branch connections 71 and 77, the piping assemblyincludes only a small number of simple, inexpensive elements. Thespacing required by the assembly is small enough so that it is possibleto dismount the rotor with great facility.

The present invention is not limited to the modifications described, butincludes all which might occur to one skilled in the art, particularlyin the details of construction of the elbow type injector having guidevanes and in the location of the impulse turbines so as to permit theuse of that type of injector, or in the elements connecting theinjectors to the manifolds which may include guide vane type elbows,preferably convergent, straight divergent pipe sections and branchconnections of various types.

I claim:

1. A nozzle for supplying water to an impulse tur bine, comprising anozzle tip, a convergent elbow for conveying water to said tip, aplurality of guide vanes extending substantially throughout the lengthof said elbow, said guide vanes being concentric with the axis ofcurvature of said elbow and dividing the flow therein into a pluralityof concentric channels, a needle valve in said nozzle tip, a stern forsaid valve extending through said vanes and said elbow to the exteriorthereof, and a fairing within said elbow on the downstream side of saidstem and extending transversely to said guide vanes, said vanes and saidfairing cooperating to reduce the tendency of the water to move in anypath transverse to the principal direction of flow.

2. A nozzle as defined in claim 1, including a spider of radial vaneslocated between said elbow and said tip, a guide bearing for said stemsupported by said spider, said spider having an axial lengthsubstantially less than its diameter.

3. A nozzle as defined in claim 1, including a guide bearing for saidstem supported at least in part on one of said vanes.

4. A nozzle as defined in claim 1, including a guide bearing for saidvalve stem, said guide bearing being supported at least in part by saidfairing.

5. Apparatus for supplying water to an impulse turbine, comprising atleast one nozzle tip, a convergent elbow spaced immediately upstreamfrom said tip, and a plurality of guide vanes each extendingsubstantially throughout the length of said elbow, said guide vanesbeing concentric with the axis of curvature of said elbow and dividingthe flow therein into a plurality of concentric channels, said vanesbeing effective to reduce the tendency of the water to move in any pathtransverse to the principal direction of fiow.

6. A nozzle for supplying water to an impulse turbine, comprising anozzle tip, a convergent elbow spaced immediately upstream from saidtip, and a plurality of internal guide vanes each extendingsubstantially throughout the length of said elbow, said vanes beingconcentric with the axis of curvature of said elbow and dividing thefiow therein into a plurality of concentric channels, and said vanesbeing effective to reduce the tendency of water to move in any pathtransverse to the principal direction of flow.

7. Apparatus for supplying water to an impulse turbine, comprising anozzle tip, a convergent elbow spaced immediately upstream from saidtip, a plurality of internal guide vanes each extending substantiallythroughout the length of said elbow, said guide vanes being concentricwith the axis of curvature of said elbow and dividing the fiow thereininto a plurality of concentric channels, said guide vanes beingeffective to reduce the tendency of the water to move in any pathtransverse to the principal direction of flow, and a straight divergentconduit section immediately upstream from said elbow.

8. Apparatus for supplying water to an impulse turbine comprising awater supply conduit, a cut-off valve in said conduit, a straightdivergent conduit section downstream from said valve, a branchconnection immediately downstream from said conduit section, a pluralityof nozzles, and piping connecting the outlets of said branch connectionto the nozzles, said piping comprising for at least one nozzle a secondstraight divergent conduit section, a convergent elbow downstream fromsaid second straight section, a plurality of internal guide vanes eachextending substantially throughout the length of said elbow and beingconcentric with the axis of curvature thereof, and a nozzle tip spacedimmediately downstream from said convergent elbow.

9. Apparatus for supplying water to an impulse turbine, comprising apair of nozzles, each nozzle including a nozzle tip, a convergent elbowspaced immediately upstream from said tip, and a plurality of internalguide vanes each extending substantially throughout the length of saidelbow, said vanes being concentric with the axis of curvature of saidelbow and dividing the flow therein into a plurality of concentricchannels, said vanes being effective to reduce the tendency of the waterto move in any path transverse to the principal direction of flow, and abranch connection for supplying water to the elbows of both saidnozzles, said branch connection having an inlet opening and two outletopenings, both said outlet openings having their axes laterally offsetfrom the axis of said inlet open-' mg.

10. Apparatus for supplying water to an impulse turbine, comprising awater supply conduit, a branch connection receiving water from theoutlet of said conduit and having a plurality of outlet openings, aplurality of nozzles, and piping connecting the outlet opening of saidbranch connection to said nozzles, said piping including straightdivergent conduit sections downstream from said branch connection andconvergent elbows between said piping and said nozzles, each said elbowincluding a plurality of internal guide vanes each extendingsubstantially throughout the length of said elbow and being concentricwith the axis of curvature thereof.

11. Apparatus for supplying water to an impulse turbine, comprising awater supply conduit, a branch connection having an inlet openingreceiving water from the outlet of said conduit and a pair of outletopenings having their axes laterally ofiset from the axis of said inletopening, a pair of nozzles, and piping connecting the outlet openings ofsaid branch connection to said nozzles, said piping comprising for eachnozzle at least one straight divergent conduit section downstream fromsaid branch connection and at least one convergent elbow between saiddivergent section and said nozzle, each said elbow including a pluralityof internal guide vanes each extending substantially throughout thelength of said elbow and being concentric with the axis of curvaturethereof.

12. Apparatus for supplying water to an impulse turbine as defined inclaim 11, in which all said pipingand said branch connection liesubstantially in the same plane.

13. Apparatus for supplying water to an impulse turbine as defined inclaim 11, including a casing for said turbine, and in which all thepiping downstream from said branch connection lies within said casing.

14. Apparatus for supplying water to a vertical axis impulse turbine,comprising a water supply conduit, a branch connection having an inletopening receiving water from said conduit and four outlet openingshaving their axes laterally oifset from the axis of said inlet opening,four similar nozzles equally spaced about the axis of the turbine, andpiping connecting the outlets of said branch connection to said nozzles,said piping comprising for each nozzle at least one straight divergentconduit section downstream from said branch connection and at least oneconvergent elbow between said divergent section and said nozzle, eachsaid elbow including a plurality of internal guide vanes each extendingsubstantially throughout the length of said elbow and being concentricwith the axis of curvature thereof.

15. Apparatus for supplying water to an impulse turbine comprising awater supply conduit; a first branch connection having an inlet openingreceiving water from said conduit, and three outlet openings havingtheir axes laterally offset from the axis of said first branch inletopening; a second branch connection having an inlet opening receivingwater from one of said outlet openings, and a pair of outlet openingshaving their axes laterally olfset from the axis of its inlet opening; afirst pair of similar nozzles, and a first pair of associated convergentelbows connected directly thereto, said first elbows being respectivelydirectly connected to outlet openings of the first and second branchconnections; a second pair of similar nozzles, and a second pair ofassociated convergent elbows connected directly thereto; divergentstraight pipe sections connected between said second elbows and theremaining outlet openings of said first and second branch connections;said first and second pairs of nozzles being grouped in a limited angleabout the periphery of said turbine; each said elbow including aplurality of internal guide vanes each extending substantiallythroughout the length of said elbow and being concentric with the axisof curvature thereof.

References Cited in the file of this patent UNITED STATES PATENTS799,809 Thomson Sept. 19, 1905 915,214 Pfau Mar. 16, 1909 1,529,632Nagler Mar. 10, 1925 1,776,392 Moody Sept. 23, 1930 1,837,901 Fottingeret al. Dec. 22, 1931 1,996,596 Smith Apr. 2, 1935 2,009,478 Coles et a1July 30, 1935

